The present invention relates generally to compensator assembly, and more particularly to submersible pump systems using one or more such compensator assemblies.
Deep-well submersible (DWS) pumping systems (also referred to as electric submersible pumps (ESP), or more simply, submersible pumps) are especially useful in extracting valuable resources such as oil, gas and water from deep well geological formations. In one particular operation, a DWS pump unit can be used to retrieve geothermal resources, such as hot water, from significant subterranean depths. Submersible pumps are driven by attached motors and generally are operable in a variety of applications in which typically both the pump and the motor are completely submersed in a well. Because submersible pumps are relatively inaccessible (often completely submerged at distances between about 400 and 700 meters beneath the earth's surface), they must be able to run for extended periods without requiring maintenance. In addition, they must be able to transfer away the significant amount of heat that is generated through mechanical and electrical losses in the pump and motor. To do that, a cooling liquid (usually oil or water) is used to fill an interior of the motor. The cooling liquid typically absorbs the heat from the motor and transfers it to the surrounding liquid in the well.
The motors of submersible pumps typically utilize a compensator that is generally connected to the motor. Ideally, the compensator performs several functions that contribute to the reliable operation of the motor, including providing for thermal expansion of the motor cooling liquid during motor operation, and balancing motor interior and exterior pressures. Conventional compensators typically are made from rubber, which are resilient and heat resistant in only limited temperature regimes, for example, up to about 110° C. By contrast, geothermal and related deep well applications may encounter temperatures of the fluid being pumped at between 120° and 160° C. Moreover, rubber compensators generally have only one maximum size due to the manufacturing or production processes. This maximum size generally is too small for high power submersible pump applications in high temperature environments (i.e., exceeding 110° C.), and is likewise not feasible for extensions or other situations where modular combinations of multiple compensators may be required. As such, there exists a need for a modular compensator operable in high temperature and high pressure environments such as those encountered in submersible pump applications.